This invention relates generally to water soluble flux compositions and more specifically to water soluble flux compositions employing polyoxyalkylene polymer vehicles which leave no residue and which are particularly suitable for processes employed in making lead-tin solder joints in integrated circuit manufacture.
Normally, large scale solder operations in the electronics industry use rosin fluxes which function to clean metal surfaces of oxides and other contaminates before soldering. Chlorinated hydrocarbon cleaning solutions are used with these fluxes which require special precautions in handling and in the disposal of spent material. Also, residues of chlorinated hydrocarbon solvents on integrated circuit structures can cause corrosion if they are not completely removed.
Water soluble fluxes have been developed to permit removal of the flux after the soldering operation with water. Such fluxes have included polyoxyethylene glycol containing materials such as are described, for example, in IBM Technical Disclosure Bulletin, Vol. 18, No. 12, May 1976, page 3988, or mixtures of polyethylene and polypropylene glycols or low molecular weight polyoxyethylene ethers along with alkyl alcohols and glutamic acid hydrochloride such as are described in U.S. Pat. No. 3,436,278.
Water soluble flux compositions have now been found which are superior to known water soluble fluxes particularly with respect to flux residue removal, viscosity control, tack quality, and the strength of solder joints obtained in integrated circuit chip joining operations.